Comparison of Relative Accuracy between Testing Semimonthly Composites or Single Random Samples of Herd Milk for Composition

Abstract

The average percent solids-not-fat ($NF) in composite milk samples was 8.95%, compared with 8.91% in their fresh milk aliquots. Testing composite samples for percent SNF by the Golding plastic bead method was equal to or superior to the gravimetric procedure. Two random tests (each 2 wks.) for herds on alternate-day delivery estimated percent milk fat as accurately as one test of a composite sample. Test differences among single random samples and the average of the fresh milk aliquots over 2-wk. periods showed variations from regression (Sy.x) of 0.13, 0.10, 0.13, 0.11, 0.08 and 0.12%, respectively for milk fat, SNF (gravimetric), SNF (plastic beads-single equation), SNF (plastic bead-milk fat interval equations), milk protein and lactose + mineral.